Contact lens



Spto 6, 1938. w. FEINBLOQM 2,129,305

coNTAc' LENS Filed Aug. 2l, 1936 2 Sheets-Sheet 1 Lemme mma/1 of maWILLIAM FEINBLOOM ATTORNEY Sept. 6, 1938.

W. FEINBLOOM CONTACT LENS Filed Aug. 21, 1936 2 Sheets-Sheet 2 INVENTCRWILLIAM FEINBLOOM ATTORNEY Patented Sept. 6, 1938 ortica contraer Lanswilliam reinbioom, New york, N. r. Application August 21, 1936, SerialNo. 97,0392

(ci. .ae-5e) 2 Glaiims.

The present invention relates to contact lenses. In my copendingapplication, Serial No. 87,577, iiled June 26, 1936, there is describeda. method of making a contact lens from a mold of the eyeball. Inpractice, the inner surface of the finished contact lens is made todiffer from the surface of the mold taken from the eye'in order that thefinished lens should fit the eye comfortably. lThis difference betweenthe two surfaces is called u tolerance and may vary somewhat frompatient to' patient. The dierence will depend on `the various forcesthat operate while the eye is in motion, and the requirement that therebe a fairly free ow of tears and oil under the lens.

When a contact lens made with suitable tolerance is placed in the. eye,it will contact the eye, through the saline solution therebetween, overa certain surface area. As the lens is continuously worn over a numberof hours, the eyelid tends to 2@ force the surface closer and closerinto the coniunctiva of the eye. This means that the forces of friction,which exist between the two surfaces Whenthe lens is first Worn, havenow been in creased and produce discomfort.

found. generates two torques; namely, one oper- 30 the lens upward. Whenthe eye moves about,

the action of these torques is to cause the lens to slide on the eye.This-sliding is of the order of a half to one millimeter and is a causeof further discomfort to the wearer. i

One of the objects of the present invention is to improve the comfortof.I the finished contact lens.

Another object of the invention is to reduce the area of friction of thesurfaceof the lens during ,w sliding to substantially a minimum.

A further object is to enable the securing of greater or less tolerancebetween the inner surface of the lens and the eyeball.

A still further object is to provide a method ofA 45 readily determiningthe tolerance required be- The movement of the eyelids, it has alsobeen' cause of the various forces acting on the lens when placed in theeye.

Various features of the invention. lie in lthe use of beads on the outersurface of the scleral portion of the contact lens, lenses havingpinhole openings in the corneal section of the lens, ltered contactlenses for excluding one or more kinds of light rays, lenses withvsuitable holes in the scleral rim for reducing suction on the lens, andbifocal, trifocal and multifocal contact 1D lenses.

Several of the foregoing objects arein general, achieved, in accordancewith the invention,

- through the use of a bead formed on the surtion with certainmathematical relations which 45 face of the lens. By means of thisbeadand/or 3 other beads suitably located, it is possible to havefriction during sliding of the lens occur only atthese beads. Thisresults in less of the conjunctiva of the eye being hit or bruised thanif there were no bead; first because less of the 20 surface area of thelens is in contact with the eye, and secondly, because friction over arounded surface like the bead may be compared, in its action, to rollingfriction rather than sliding friction. 25

Other objects, features and advantages of the invention will ,appearfrom a reading ofthe following detailed description Which is accompaniedby drawings, wherein:

Fig. 1 illustrates, in cross section, one embodi- 30 mentcf acontactlens in accordance with the invention as it would appear lover aneyeball.

Figs. 2 to 9 illustrate other views of contact lenses made in accordancewith the principles of the invention. These figures are the bottom 35views of the contact lenses. Figs. 2, 3, and 7 illustrate beads on thecontour of thev lenses, which are not of uniform shape. Figs. 4, 5, and6 illustrate beads in the form of thin raised surfaces on the scleralportion of the lens. Figs. 7, 8, and 9 illustrate contact lenseswhereinV the corneal portion is a multi-focal lens.

Figs. 10. and 11 are given for theoretical considerations and will bediscussed later in connecprovide a method of determining the propertolerance".

Referring to Fig. 1, .there is shown a finished contact lens I restingon an eyeball 2 with the usual'saline solution between the inner surfaceof the lens and the surface of the eye. This contact lens may,` ingeneral, consist of any suitable material, such as glass, although it is-preferred that the scleral portion be made from a resin, such as aBakelite composition, in the manner set forth in my copendingapplication, supra. The invention, it is to be distinctly understood, isnot limited to a lens whose scleral rim is made from any particularmaterial.

Contact lens I is shown provided around the contour of its inner surfacewith a rounded ring bead 3, which enables friction between theeye andcontact lens to occurduring sliding only at and` over the roundedsurface of the bead. In this particular location of the lens, the beadmay also have a rounded extension on the outer surface ofl the lens, asshown, to provide a sliding action of the lids over the lens. The beadmay be located anywhere on the inner surface of the scleral rim of thecontact'lens, so as to provide for the rolling friction rather than the"sliding" friction and, if desired, more than one bead may be providedanywhere along the inner surface of l the contact lens so that they door do not overthe lens and adjacent tissue.A

tion. Pig. 3 shows another similar arrangement,

lap each other in their lengths, in which case each of the several beadsneed not be entirely continuous. These beads may also be radial,parallel, or skew in position, and may have any rolled form, either onthe inner surface or outer surface of the lens to reduce frictionbetween An important advantage of the ring bead .I is that it provides adesirable method of vnils-- chanicallyobtaining greater or lesstolerance" between the inner surface of the lens I and the eyeball 2.Thus, by varying the amount of proiection of the bead 3 it is possibleeither to increase or decrease the "tolerance at any particular place inthe eye, or uniformly over the eye. Heretofore, it has been. possible,as described in my copending application Serial No. 87577, to obtain adesired degree of tolerance", for example, 0.020 of an inch, by coveringthe mold of the eyeball with tinfoil of 0.020 of an inch thickness, andhave the contact lens molded on this tinfoil. In accordance with thepresent invention, the same tolerance can be obtained by providing aring "bead at the contour of the lens which extends from the innersurface of the lens towards the eye to an extentV of 0.020 of an inch.`Of course, a combination vof the above two methods of obtainingtoleranceI may be used. The choice of which of these three methods touse 'for obtaining "tolerance will depend on the total amount oftolerance" desired, and the type of eyelids or lid action p resentin theparticular eye. f

Fig. 2 illustrates a bottom view of a contact lens made in accordancewith the invention and shows that the rln'g "bead" need not be perfectlyuniform throughout its length but may be wavy orha've different sises inthree dimensions. The bead, it will be evident, may also consist ofseveral separate portions 3,4' and l, as in Fig. 2,

so as to'form channels or corrugations therebetween, in lwhich case wehave a way of reducing the suction on -the lens. The saline vsolution.

betwetneeyeand the lens, it will be round, will not flow out entirely,due to capillary attracwherein a plurality of raised beads I, 0 servethe same purpose as the beads of Figs. 1 and 2.

If desired, the suction holding the lens on the eye may also be reducedby piercing the scleral rimof the lens with one or more properly formedholes 4, of any shape, which are suitably rounded at the edges, as shownin Fig. 2. l

Figs. 4, 5, 6 and 7 illustrate various forms which the beads may take,either on the inner or outer surface of the lens. In Figs. 4, 5, and 6the beads are thin.'straight, raised surfaces 1, l. in Fig. 7 the beadtakes the form of an irregular raised surface 8. l

One of the important features of the invention comprises a contact lensmade from a mold of the eye, and having suitabletoleranceasdetermined bythe torques and forces acting on the lens when in the eye, and soconstructed that the lens touches the eye at a minimum number of pointsunder all conditions, particularly ,during sliding. Although theinvention has mentioned the use of beads, it should be understood that acontact lens made from the mold of the eye and modifiedj so that thecurvature ofthe entire lens or merely the curvature of the lower edge ofthe scleral rim yis less than the curvatures of the correspondingportions of the eye, for the purpose of having the lens contact the eyeonly at certain points, or at the entire lower edge of. the rim, iswithin the spirit and scope of theinvention. l

It has been observed that there is a best size for the bead, appreciabledeviations from which will either make the lens too tight on the eye andcause pain, or make the lens too loose. The preferred ymethod of makinga contact lens with a bead on the inner surface, although the inventionis not limited thereto, is to form a plaster or stone cast or mold froman impression taken of-the eye, and to provide an indentation in saidmold at the location it isi` desired to place the bead, and from suchindented mold obtain the finished contact lens, in accordance with theteachings set forth in my copending application. The depth of theindentation may correspond to or begreater-than the depth of tolerancerequired. since suit'able grinding or polishing of the solei-a1 rimofthe contact lens may be resorted to in order to obtain a particularsize of bead.

The lessential steps of this particular method, involves (a) takinganimpression of the eye with wax or with a 4hydro-colloici solution knownby the trade naine Negocoll, (b) forming a plaster or stone mold (hereindesignated the positive) from this impression, (c) depositing a 'layerof wax on the positive mold of suitable thickness, which is somewhatgreater than the' vwill at this stage have adhered to the upper half.)(i) cutting a groove in the positive mold from .which the wax has beenmelted off, for the bead,

andagain tinfoiling the positive, (i) placing the ground synthetic resin(auch as Bakelite) in the space between .the positive and negativemolds.

and (lc) closingthenaskandvulcanisingorbab' ing the flask and-contentsat a suitable tempera'- ture for a desircdperiod of time.

Wherethebeadistobeplacedontheoutersurfaxceofthelenaachsngeshouldbemadeinthe foregoing step (c) which willinclude depositing additional wax on the locations where itl is desiredthe bead should be. Alternatively, an additional thickness of wax may beadded at this particular step and the outer bead formed by `grinding thefinished lens.

At this time it is to be distinctly understood that the invention is notlimited to the foregoing between eyeball and lens be substantially amini- Although the matter of tolerance has been very generally mentionedherein, the following enables one to compute the corrections requiredfor various types of eyes on account of the forces acting on the lens. iI have found that when a contact lens is placed in the eye, it is actedupon by various forces and torques that tend to change the orientationit would otherwise possess with reference to the eye. This will resultin excess pressure being exerted on some parts of the eye, and unduelooseness elsewhere. To properly care for this situation it is necessaryto allow certain tolerances (i. e., change curvature of inner surface ofcontact lens) that will cause the contact lens to be some predetermineddistance (e. g., 0.6 mm.) from the eye at all points after the actin ofthese forces and torques. These corrections will now be considered indetail.

I. Anterior-posterior correction When both the eye and lids arestationary, three following forces keep the contact lens in equilibrium:

Va. Force due to atmospheric pressure.

b. Force due to lid pressure.

c. Force due to pressure of water between eye and contact lens.

Referring to Fig. 10, it will be noted that the answer is anothersurface (SN) identical to the i'lrst (So), and merely translated acertain distance, d; Practically the` second surface SN must be obtainedfrom the rst by adding tinfoil to a plaster cast of same, and buildingit up to the new surface. Since burnished tinfoil lies on a surface sothat its maximum thickness at any point lies normal to surface, it isobviously necessary to make a computation of one thickness (X) oftinfoil as a function of the radius of curvature (r) at the point, andthe height (h) of the point from the axis of translation (O-O): Thefollowing calculation is perfectly general and may be applied to anysurface where the radii of curvature and the hs are generally known.However, for simplification, it will be assumed thevsurfaces arespherical.

v tions.

Hence X is'known as a function of the param-` eters r, h, and'd. f

As a simple illustration let 1': mm. d=0.6 mm.

then the following schedule may be prepared from 3.

r mm. d mm. h mm. z mm,

The rightmost column indicates the actual thickness of tinfoil to be puton the plaster model 0f So on the various zones so as to produce SN.

It was found useful to employ auxiliary formulae to save time inperforming these calcula- One was to determine small changes in X due tochanges in d alone.

From` 3; 4.

'I'his formula is used as a computing gage to .determine the thicknessof the second coating of tinfoil .for the positive mold, to obtain thedimensional requirements forthe inner surface of the contact lens inmaking a mold in accordance with the preferred method as outlined above(step and in my copending application, supra.

II. Vertical torque correction (horizontal forces 'about vertical axis)In obtaining the value of the correction for vertical torque, let usconsider a thin portion or shell of the contact lens between twoparallel horizontal planes which pass nearly through the center of thecornea, `particularly in connection with Fig. 11.

In considering the action of the lids on the thin lens shell as theyclose, it willbe assumed that there exist normal forces acting on theshell (due to lid) that are a minimum at the temple (T) and a maximumatggthe nasal (N) portion.

It is desired to compute the torque uthat thisgradient distributiongenerates about the center of gravity (Ps) of the thin shell (assumedspherical).

'I'he torque about Ps may be defined as 4 where lrPxPs is the radiusvector from the center of gravity to the portion of thin shell (treatedas a set of particles)v Px, and

IFM

is the force exerted on Px by the system B (eyelid). l

For computational simplicity it will be assumed that IF increases inmagnitude linearly with the distance h.

Then:

x1 being a proportionality constant.

The summation may be replaced by an integration, and

f=IK1(l-cos 050,1 sin 61; n. =|rpxp8` In triangle oPsPx l f ZK1x(cos-cos 6)6 o I Y P. mmxlt It will now be assumed that this torque causesthe thin shell to undergo a small rotation A9 about the center ofgravity. The energy for this rotation-comes essentially from the motionof lids when they close. The lids will be assumed to exert a irictlonalforce `on the shell, and to move through a distance of 1 mm.approximately. The work done by the lids will be taken as the product ofthis frictional torce and this displacement of 1 mm. This frictionaltorce may be compared with the force'exerted by the `water between thelens and the eye. Thelatter is represented by@v f rd (a calculationsimilar to the one presented above.) Assume:

mg=wexgnt 1 ee. or'war).

Prictional force This 'formula is med. together withother formullesetforth hereinafter, indeter'mlnlng the net tinfo'iling and reliefcorrections which are applied in step (i) mentioned above.

The values for B1. Ka were estimated from Y practical experience. Atypical calculation mayl Net Net Radius rmm. armut) Xmm. mk grd mm bemade with Ka=2, K1='I.5 (dg) yielding following schedule.

It is now assumed that this rotation, which`wil1 cause the lens to digin at the nasal portion and be loose at the temple portion, may beneutralized by positively tinfoillng the amount indicated in therightmost column in nasal portion, and negatively'tinfoiling the samequantities on the temple side. This'amounts to addition and'subtractionofthis correction to the anterior-posterior correction to obtain the naltolerance desired in this shell. In other words, where the lens wouldordinarily dig in at the nasal portion and stand away at the templeportion, it is necessary to effectively remove enough material from theinner surface of the nasal portionof the lens and add material to theinner surface oi' the temple portion of the lens to iill in the gapwhich previouslyexisted. This removal of material may be termed positivetolerance and is, in practice, actually obtained by suitable tintoiiingin the foregoing step (i), whereas the addition of the material in orderto i111 in the gap may be termed negative tolerance and is, in practice;obtained in the same step (i) of theprocess by scooping out or relievingthe'surface'bftlreplaster positive cast or mold before the tinfoiling.

lIII. Horizontal torque correction (vertical forces about yhorizontalaxis) vertical torque except for the constants K1 and A Ka. Aftersuitable values for K1, K: are selected, the tolerances may becalculated. As an illustration, a typicalset oi' values would be K1=2.K:=2.

The vertical and horizontal torque corrections are functionally of thesame nature as the anterior-posterior correction, and, with the latter,are used to determine the net thickness of the second coating of thetinfoil to be placed on the positive mold.

In the entire discussion above, it has'been assumed that sphericalsurfaces properly represent the eye. 'I'his is entirely different fromwhat has been discovered by actual measurements. A method :lo'robtaining the curvature distribution *.of the eyeball (sclerai portion)was employed to obtain the proper radius in any particular meridian.'I'he method was to employ a magnified, opaque projection of a plastercast (of the livixa eye) in anydesired meridian.

In computing the horizontal and vertical turques. the value oi.` Kawhich has given best resuits has been 2.0, while for both torques thevalue of K1 may vary substantially between 3.5

and '1.5, the exact value of which may be determined by learning theproper tolerance of the lens in one meridian, asby examination of theloose portion' of a lens perfectly adapted to the mold oi' the eye afterbeing placed in the eye and acted upon by the above mentionedA forces.'nie extent oi' rthe looseness is precisely the negative alaasoetolerance" required in that meridian. Since the anterior-posteriorcorrection in that meridian is known for all eyes, this correction maybe subtracted from the above negative tolerance and,

the remaining tolerance may be substituted in the formulae involving K1to determine the value of this constant. This value of K1 may then beused to determine the tolerance in all other (eight are usuallysufficient) meridians of the same eye. Inasmuch as there are two torquesinvolved and the value of K1 will be diierent for each torque, then thelooseness must be observed in the temple portion of the eye for thevalue K1 for the vertical torque (horizontal forces) and in the inferiorportion of the eye fr the. value of Kr for the horizontal torque(vertical force).

The contact lens, preferably made from a mold of. the eye in accordancewith the teachings outlined herein, and preferably provided with one ormore beads, finds convenient application to certain cases Where it isnecessary that the glass corneal section contain a filter, especially incases of marked photophobia (intolerance to light), cases of albinism,or Awhere the contact lens is to be usedunder conditions of excessivelight, such as mountain climbing, seashore, water and snow glare.

The use of colored illt'ers in the glass portion may also be used tochange the color of the iris in the eye, so that by a suitableselection, a

blue-eyed person may be made to appear brown.

eyed. i

Another variation of this filter-in the corneal i opaque, except for asmall clear portion of the periments in physiological optics.

'Ihere .are certain cases where the solera of the eye lacks sufhcientpigment, resulting in light entering the eye through the-sclera` This istrue in cases of4 albinism. It is proposed to tint the transparentscleral portion of the contact lens vwith a suitable coloring material,or to make such scleral portion of an opaque material.

Another use lfor the contact lens, as designed above, is in cases ofdeformed eyes, due to anomalies at birth or subsequently injury. In suchcases, as well as in cases of crossed eyes, the corneas are turned in,out, up or down. It is possible, by properly displacing the cornealglass section of the contact lens,`to make the eye appear as though itwere perfect.

biiocal correction.

Other applications of the invention lie in the use of contact lens'eswhose corneal sections are made with two or more different refractivepowers. In many cases it is required to have a rlhis bifocal ortwo-vision glass can be made in this contact lens by using for thecorneal lens portion a lens, the upper part of which is fittedfor thepatients distance vision, the lower part of which is fitted for thepatlents reading vision. Such a lens, preferably made from a mold of theeyeand provided with one or more beads, is shown in Fig. 7.

In the same way, it isl possible to make the corneal section of three ormore different refractive sections. Such lenses are termed trifocal ormultifocal lenses. Examples of these are shown in Figs. 8 and 9, and mayinclude one or more beads" on the surfaces of the scleral rim in themanner shown in any of the Figures 1 to 7.

By the term bead, as used in the foregoing description and appendedclaims, it is to be distinctly understood is meant any projection orraised portion of any shape whatsoever which extends from an absolutelyuniform surface of the lens. Thus where discontinuous beads are used,the beads may comprise triangular projections whose apices are rounded.which projeci `tions protrude from an otherwise uniform inner or outersurface.

What is claimed is: 1. 'A process of producing a contact lens whichincludes the steps of obtaining an impression of the eye, forming a moldfrom said impression.

providing an indentation in said mold for the purpose of forming a beadon the inner surface of the scleral portion of the lexis, depositing asuitable layer of wax and an overall metallic lay- I er on said mold,investing said covered mold in` a flask, effecting evacuation of the waxto pro- ,i

duce a metal walled negative whose internal dimensions generally conformwith the outer` surface of the scleral portion' of said lens. fillingthe metal walled negative with suitable material to form the scleralportion of said lens, forming from the original mold a metallic linedmodel whose external dimensions generally conform to the dimensionalrequirements of the inner sur- Aface of said lens, and hardening'saidsuitable material to conform with the internal dimensions of saidnegative and the external dimensions of said metallic lined originalmold, to form the lens.

2. A contact lens comprising a glass corneal lens portion and a .scleralrim portion of moldable synthetic resin shaped to rest on the sclera ofan eye' to hold the corneal lens portion in position before the cornea,said scleral rim portion having its contacting surface formed withprojections and depressions so that only th projections contact thesclera and the area of contact is thus reduced.

WILLIAM FEINBLOOM.

